Immune response of rabbits to native G-actins

Actins are highly conserved proteins and are therefore claimed to be not very immunogenic without prior denaturation or chemical modification. We have obtained in rabbits high-titered antibodies to "native" G-actins from chicken and man, and assayed their cross-reaction using an enzyme immunoassay, Western blotting and immunohistochemistry. The antigens differ in their ability to induce antibody formation (chicken gizzard actin [(beta), gamma] greater than chicken skeletal actin [alpha] = human platelet actin [beta, (gamma)]). Antibodies to skeletal actin [alpha] are muscle-specific and mainly directed against the homologous region comprising the N-terminus (residues 1-226). Antibodies to gizzard actin [(beta), gamma] cross-react, to a lesser extent, with the alpha and beta, (gamma) isoforms. They show no regional specificity within the homologous antigen. Antibodies to the tryptic core fragment (residues 69-374) of skeletal actin react with fragments comprising the C-terminal part of muscular actins. Antibodies to platelet actin [beta, (gamma)] cross-react with muscular actins, recognizing not the native, but slightly degraded molecules. Platelet actin induces the formation of high-titered albumin antibodies for hitherto unknown reasons.